Fuel injection pum mechanism



Nov. 12, 1946. l.. JOHNSON FUEL INJECTION PUMP MECHANISM Filed April 19,1943 4 4 w Z 6 3- 5 Z 5 4 Wm y Z, 7. f d. Z. L A s INVENTOR. l. /ayd EJohnson BY ATTaRAY,

Patented Nov. 12, 1946 FUEL TNJECTToN PUMP MEcnANTsM Lloyd E. Johnson,Fon du Lac Township, Tazewell County, Ill., assignor to CaterpillarTractor Co., San Leandro, Calif., a corporation of California fApplication April 19, 1943, Serial No. 483,633

4 Claims. 1

My invention relates to fuel injection mechanlsm, and more particularlyto such mechanism adapted for injection of relatively low viscosity fuelinto an internal combustion engine.l

In fuel injection systems for the injection of a relatively lowviscosity fuel, such as gasoline, into an internal combustion enginewhich is provided with pumping mechanism for injecting the fuel intoeach cylinder of the engine, in a. so-called solid stream, there is theproblem of precluding leakage of the fuel past the fuel injection pumpplunger during the injection stroke thereof. This is so because arelatively low viscosity fuel, such as gasoline, is also usually quitevolatile except for a small portion of a gummy nature; and if it were toleak past the pump plunger, evaporation would cause a gummy deposit thatwould impede eflicacious operation of the plunger in the pump cylinderwithin which the plunger is adapted to work.

This problem does not exist so much with Diesel fuel oils of relativelyhigh viscosity because the relatively high viscous nature of the oiltends to preclude the leakage. Furthermore, relatively high viscosityoils are usually of a relatively low volatility', yand therefore do nottend to cause as much gumming as do relatively low viscosity'and '4relatively highly volatile fuels, such as gasoline. Also, a relativelyhigh viscosity Diesel fuel oil has some lubricating properties which ifa low rate of leakage should occur. will result in desirable lubricationbetween the working surfaces of the cylinder and the plunger, which isnot true with more volatile fuels. such as gasoline, which tends todilute and destroy whatever lubricant is employed for the plungeraction.

In the past, provision has been made to preclude such leakage ofrelatively low viscosity fuels, by introduction of a relatively highviscosity lubricant between the pump plunger and the cylinder wall.However, in prior constructions with which I am familiar, the leakageprecluding lubricant has been introduced through the Wall of thecylinder within which the pump plunger works. Such arrangement is notdesirable because of the difficulties encountered in making a suitableconnection between the cylinder and the housing containing suchcylinder, for the introduction of the sealing lubricant.

My invention is designed to overcome this problem by the provision ofimproved means facilitating the introduction of the sealing lubricant;lwhich is of such character as to enable the sealing lubricant to beemployed for lubricating the location of engagement between the pumpplunger and actuating means therefor, and to lubricate the bearing meansfor the pump plunger actuating means; and which is of relatively simpleand economical construction. Other objecis of my invention will becomeapparent from a perusal of the following description thereof.

Referring to the drawing:

Fig. 1 is a transverse vertical sectional view .of a form of fuelinjection pump mechanism containing the construction of my invention.

Fig. 2 is a horizontal section taken in a plane indicated by line 2-2 inFig. l.

Fig. 3 is a horizontal section taken in planes indicated by lines 3-3 inFig. l.

Fig. 4 is a horizontal section taken in .planes indicated by lines I4 inFig. 1.

Fig. 5 is a horizontal section taken in a plane indicated by line 5--5in Fig. 1.

The lubricating and sealing means of my invention may be employed inassociation with any type of fuel injection pump wherein an impellerlocated in a pump housing is operated by suitable actuating means. Forpurposes of explanation,

it is shown in the form of fuel injection mechanism illustrated in Fig.l. Such injection mechanism includes injection housing means comprisinga tappet and camshaft casing 2 to which a pump casing 3 is detachablyconnected by studs 4 and nuts 6. Adjacent the fuel discharge endthereof, pump casing 3 is formed with an internal shoulder I againstwhich is clamped check valve cage 8 containing spring thrust check valve9; such clamping being through a removably mounted plunger barrel orcylinder II which is clamped in position by means of nut I2 screwed inthe inside of casing 3 against shoulder I 3 formed on cylinder II; asuitable sealing ring Il being interposed between nut I2 and shoulderI3. In this connection, nut I2 is formed with inwardly extending slotsI6 to enable it to be engaged by a suitable tool for screwing andunscrewing of the nut when y so desired. To hold cylinder II againstangular or turning movement, a cap screw I1 screwed into casing 3, isprovided with an end extension I8 engaging in a recess I9 formedadjacent the head of cylinder I I.

With respect to multiple cylinder engines, a plurality of individualinjection pumps, one for each cylinder of the engine, is employed; andthe injection mechanism housing means contains all of such pumps and themechanism for actuating the saine.l A longitudinally extending fuelinlet passage or manifold 2| is formed in pump casing 65 3, and receivesa constant Supply of fuel at a relatively low pressure of about fifteen(15) to twenty (20) pounds per square inch, fed into it by a fueltransfer pump (not shown) as is customary in the art, and whichcontinuously circulates the fuel from a fuel tank (not shown).Communicating with fuel inlet passage 2| is a fuel inlet orifice or port22 formed in the wall of the head of each pump cylinder Il; the cylinderwall having a short bleed passage 23 therethrough which communicateswith inlet port 22 and with the inside of cylinder Il for a purpose tobe subsequently explained.

Slidably mounted in cylinder I| for axial reciprocation therein is apump plunger 24 which is preferably of the type wherein the quantity offuel fed or injected past check valve 9 is controlled by angularadjustment or rotation of the pump plunger about its axis. For thispurpose, plunger 24 is formed adjacent its discharge or injection endwith annular groove 25 around its periphery, which communicates with anaxially extending groove 21 adjacent a slanting or scroll edge 28adapted to work past port 22 as the plunger is reciprocated andangularly adjusted. The fuel discharge end of the plunger is flat, andat a right angle to the axis of the plunger.

Thus, as the plunger is reciprocated by suitable actuating means, andangularly adjusted through suitable engine governing means, metering offuel injected by the pump is controlled in a well-known manner. Whenpump plunger 24 is actuated on its compression stroke to inject fuelwhen port 22 is closed as the plunger works therepast, the pressureimparted to the fuelmay be as high as two thousand (2,000) to fourthousand (4,000) pounds per square inch. In Fig. 1, the angular and theaxial positions of plunger 24 are shown substantially at the terminationof injection, as slanting edge 28 is just about to uncover inlet port22.

Actuating means in the form of tappet mechanism 29 is provided in casing2 for imparting the injection or discharge stroke to plunger 24. Each ofthe tappet mechanisms in casing 2 comprises a sleeve 3| having anintermediate partition wall 32 secured therein by any suitable means,such as welding, and which is slidably mounted for axial reciprocatlonin a bearing wall surface 33 formed in casing 2. A cam follower roller34 is located at one side of wall 32 and is journalled for rotationabout a pin 36, on suitable roller bearings 31; the roller 34 engagingcam 38 on longitudinally extending camshaft 39 which is adapted to bedriven from the engine.

The opposite side of wall 32 is formed with a at surface adapted to befreely engaged by a flat end surface 4| formed on the tappet end portion42 of plunger 24. Thus, as the plunger is moved axially by the tappetmechanism, it may be readily turned angularly for the purpose previouslyexplained. It will be noted from Fig. 4, that the tappet mechanisms 29are provided with fiats 43 on their sides; and a pin 44 is positionedbetween the flats of adjacent tappet mechanisms 29, so as to hold suchmechanisms against rotation or turning as they are reciprocated.

For effecting the return or suction stroke of plunger 24 after thedischarge stroke, a spring 45 is interposed between nut I2 and a springretainer 41 at the tappet end portion 42 of the plunger. Spring retainer41 is provided with an inwardly extending slot 48 to enable it to beslipped over plunger 24, and is adapted to be thrust against a shoulder49 on the plunger, and an end 5| of tappet sleeve 3|. When spring 45thrusts retainer 41 against sleeve end 5| on the return stroke of theplunger, the spacing between the surface on shoulder 49 adapted toengage retainer 41 and the flat surface 4| at the tappet end of theplunger, is such as to provide a slight clearance between wall 32 andretainer 41, thus enabling plunger 24 to be angularly adjusted withease.

The means for enabling angular adjustment of the plunger while it isaxially reciprocated lncludes a gear sector 52 which is split at 53, andrigidly clamped to plunger end portion 42 by means of cap screw 54. Theteeth on gear sector 52 engage a rack 55 which is slidably mounted in arecess in casing 2 between such casing and pump casing 3; a recess 55being formed in sleeve 3| to allow engagement between such gear teethand the rack. Rack 55 is connected to suitable governing means (notshown) operated from the engine.

To seal against leakage past the plunger of relatively low viscosityfuel which the pump may inject, I provide an interior passage 51 in thepump plunger for conducting lubricant between the plunger and thecylinder wall, at a pressure above that at which the fuel is supplied bythe transfer pump through inlet port 22 but considerably below the fuelinjection pressure; such lubricant pressure being preferably abouttwenty (20) to thirty (30) pounds per square inch. Be-

cause of the higher pressure of the sealing lubricant, compared to thatof the fuel supply pressure, an emcacious seal is obtained. Furthermore.the lubricant will also serve to lubrlcate the working surfaces of theplunger and the cylinder. In this connection, it will be noted that thetappet end portion 42 of the plunger extends beyond the tappet end ofcylinder throughout the entire stroke of the plunger. Such arrangementenables interior passage 51 to lead to the flat end surface 4| of theplunger for supplying of lubricant thereto at that location, which makesfor a simple construction. Intermediate the plunger ends, passage 51terminates in radially extending orifices 58 communicating with aperipheral groove 59 formed in the plunger. Thus a sealing ring of fluidwill be maintained in groove 59 as sealing fluid is supplied throughpassage 51.

For supplying fluid to passage 51, I provide a. passage 5| in tappetpartition wall 32, which is open to a side of tappet sleeve 3| adjacentone end, and which includes an orifice 62 at its opposite end incommunication with passage 51. As fluid flows from tappet passage 5|into plunger passage 51, the location of engagement between the plungerand its actuating means will be well lubricated, which facilitatesangular adjustment of the plunger when tappet wall 32 engages plungerend surface 4I during the injection stroke of the pump.

Means is provided for continuously pumping lubricant through passages 5|and 51, and at the same time lubricating bearing 33 in which the tappetmechanism slides. Casing 2 is adapted to contain a supply of lubricantwhich is continuously fed by means of a pump 53 including meshing gears54, one of which is driven from camshaft 39. The pump gears drawlubricant into the pump through inlet passage 55, and dischargelubricant through passage 51 which communicates with a lubricant feedmanifold or passage 68 in the inside wall of casing 2 adjacent tappetsleeves 3|. A suitable pressure relief valve -69 communicates withpassage 61. Feed passage 68 is open to sleeve 3| and the portion ofsleeve 3| adjacent feed passage 68 is formed with a recess 1| whichcommunicates with passage 6|. Such arrangement allows free flow oflubricant into passage 6|; and at the same time, the lubricant willlubricate bearing 33.

During injection of fuel at the previously mentioned high pressure,leakage might occur past the plunger irrespective of the sealing fluidin groove 59, but this is prevented by the previously mentioned bleedpassage 23. The inner end of passage 23 is in such position that duringthe time fuel is actually injected by the pump plunger, it communicateswith a peripheral groove '|2 in the plunger, which is located betweenthe injection end of the plunger and sealing uid groove 59. As a result,high pressure injection fuel can only leak past the plunger as far asgroove 12, as passage 23 will bleed the pressure off to the low pressurewhich obtains in fuel inlet manifold 2|.

Although the construction of my invention is particularly adapted foremployment in fuel injection pumps adapted for the injection of arelatively low viscosity fuel, such as gasoline, to be supplied to sparkignition engines, it may be used, if so desired, in Diesel orcompression ignition fuel injection pumps where relatively low viscosityfuel oil is employed, and leakage thereof past the pump plunger mightprove detrimental.

I claim:

1. Fuel injection mechanism comprising a. pump cylinder, a. pump plungerreciprocably mounted therein, a reciprocable tappet member engageablewith an end of the plunger. a bearing wall for guiding said tappetmember, and lubricating means comprising passages through the plungerand tappet for supplying lubricant to ond circumscribing recess spacedfarther from the head of the plunger, and means for supplying lubricantunder pressure to said second recess.

3. Fuel injection mechanism comprising a pump which includes a plungerreciprocably mounted in a cylinder for transferring fuel in meteredquantities from a source of supply to an engine, said plunger having acircumscribing recess spaced from its head and communicable with saidsource of supply for return thereto of fuel leaking past the head of theplunger, a second circumscribing recess spaced farther from the head ofthe plunger, and means for supplying lubricant under pressure, exceedingthe pressure of the source of fuel supply, to said second recess.

4. Fuel injection mechanism comprising a pump which includes a plungerreciprocably mounted in a cylinder for transferring fuel from a sourceof supply to an engine, means for relieving pressure on fuel leakingpast the head of the plunger, and means for supplying lubricant to thecylinder walls at a pressure exceeding that of the leakage fuel.

LLOYD E. JOHNSON.

